PSI - Issue 5

Victor A. Eremeyev et al. / Procedia Structural Integrity 5 (2017) 446–451 Eremeyev et al. / Structur Integrity Procedia 00 (2017) 000 – 00

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Fig. 3. Nodal displacements of user elements.

In this research to visualize the stress distribution in continuous 3D user elements two different approaches are recommended. In the first approach the 3D graphical program based on OpenGL library have been developed (see Wright and Sweet, 1996). This is a very ambitious task which requires high-level programing skill in Microsoft Foundation Class (MFC) and OpenGL libraries. The OpenGL library allows for writing very effective code to display sophisticated 3D graphics which is being accelerated by the hardware. Such features as: 3D space transformations, depth buffer, color and shading, lighting and lamps, double buffering etc. allow the programmer to concentrate on crucial part of the numerical code without going into technical details about the hardware. In practice, own graphical programs may be more comfortable than the commercial ones mostly because they can be easily modified according to the user needs. In the second approach the special Python script is developed for the ABAQUS visualization module. In ABAQUS program all the user activities resulting from menu, trees or dialog boxes actions are exchanged into appropriate Python commands executed by the ABAQUS kernel. The ABAQUS engineers have been extended the standard Python script language by numerous ABAQUS objects. In the case of postprocessor the following objects are available: output database, part, material, section, type of analysis, finite elements, boundary conditions, displacements, stress tensor and many others. These objects own their data and methods which operate on these data. Thus, the method which saves the output database object to the binary file, forces saving to this file all postprocessor objects (mentioned above) created by the Python script. This way fully-functioning output database is made which does not differ from the database generated by the ABAQUS solver. This task requires good knowledge of object oriented programming (in particular Python language), and good knowledge of ABAQUS objects. The advantage of this approach is that all the ABAQUS visualization module features are available for the user. Similar but less effective technique to visualize results of user elements has been implemented by Roth et al., where the results obtained for ABAQUS built-in elements have been replaced by the Python script by the results of user elements.

4. Benchmark tests

As the benchmark test the contact between cylinder and two flat plates is considered. Because of the problem symmetry only one plate and the half of the cylinder is considered. Both parts are meshed by hexahedral or by tetrahedral linear finite elements. The cylinder is meshed by user elements developed for micropolar approach while the plate is meshed by ABAQUS built-in 3D finite elements. The nodes-to-surface contact in assumed. The FEM mesh consisting of tetrahedral elements is shown in Fig. 4.